A few weeks ago, the YouTuber who goes by Warped Perception published a video showing what goes on inside a car tire while driving. That same channel now has a new video that also shows the innards of a tire, but instead of motoring down the road, the car is sitting still while its rear tires are ripping a huge, smoky burnout. The footage of the rubber exploding is glorious. Watch it and read a tire engineer’s take on what’s happening.
What we have here are classic ingredients for a viral video: Choose a “mass appeal” subject that a vast majority of people interact with regularly (car tires), provide unique insight that answers a question that most people didn’t realize they were curious about (“What does the inside look like?”), and wrap it all up in a highly visual package (GoPro footage of the tire in action). It’s this formula that led Jalopnik’s “Here’s What It Looks Like Inside A Tire When You Drive” story and the YouTube video itself to reach such large audiences, so it’s no surprise that there’s now a follow-up video.
This one shows the inside of a tire during a burnout:
As in the driving video, the burnout footage shows the inner liner of the tire. The GoPro is aimed at a section of tire that flexes each time that section comes into contact with the ground and takes up the vehicle’s load.
The view from the outside shows the rubber tread heating up, producing smoke, and tearing itself—as well as the steel belts—into bits.
Of course, even though this is just a YouTube clip, and I could simply write “Hey folks, watch this viral video!” You didn’t really think I was going to write about something as technically interesting as a failed tire without providing a bit of nerdy technical insight, did you?
Of course not.
I emailed a few engineers about this video, and one of them—who works for a major tire manufacturer—gave a great description of what happened. He began by giving a quick rundown of basic tire construction. “First off- tire construction,” he wrote in an email. “Tread then nylon cap then steel belts then polyester radial plies then butyl inner liner.” With that established, he noted the initial condition of the the tire in the video. “The tire tread is completely worn to start with,” he wrote. “The nylon cap is already showing, so there’s not much rubber there for a long-lasting burnout.” Indeed, he is right:
With screenshots attached, the tire engineer gave a play-by-play of what happens in the video at each key moment. “He spun the tire until there was no tread, then wore through the nylon cap which helps hold the belts down, then the belt actually separated away from the polyester carcass, you can see the separation in the shoulder of the tire where the belts completely delaminated from the polyester radial carcass,” he wrote to me.
“This was likely a case of wearing down through the nylon cap then actually just spinning the belts on the ground and ripping the belts from the carcass, and/or creating so much heat that the belts separated from the carcass at the belt edge. Either way, the belts are flapping around in the slow-mo part of the video for some time…can’t argue that!”
Things then got even nerdier.
“Note that earlier, before the burnout, the inner liner was relatively smooth, just the radial lines from the bladder are evident inside the tire indicating a traditional tire manufacturing process:
“Just before the tire blows, you can see below that the inner liner is starting to get some indents right at the crown near that ‘R20' marking (likely a tire inspector stamp),” he continued, “indicating that either the belts flapping around or the rough asphalt was pushing in on the tire carcass.
“There were no belts attached to the tire in this area any longer protecting the tire carcass from puncturing and losing air pressure. The belts were already flinging around and nearly completely separated from the tire carcass at this point.”
Then the enginerd then began describing what he thought to be the cause of the failure, which occurred at the center of the tire tread. “The polyester carcass and butyl inner liner actually gets worn and/or ripped near that “R20” spot where the dimples are forming, then ‘explodes’ in the sense that the air rushes out. You can still see the flap of rubber with the ‘20' next to the go-pro. The tire was super hot, you can see it smoking, so the inflation pressure of the tire was likely higher than normal as well since pressure goes up with temperature, which further contributed to a more [violent] rush of air leaving (the ‘explosion’).”
Our expert tire engineering source then described the failure further, providing a reason for why it occurred where it did:
When a tire is driving (as opposed to braking) most of the forces are in the center of the tread, and without any belts, the inflation pressure within would want to make the tire balloon-shaped since there is no opposition from the belts which serve to protect the tire and provide a flat contact patch. With that said, it’s no surprise that the tire’s polyester cords were ripped right in the center of the tire where all of the force was, combined with grinding the polyester on a very coarse concrete surface. You can see in this image tha[t] the polyester [cords] were ripped in a circumferential line with the direction of wheel spin, as they are frayed at the ends. As soon as a few of the polyester cords failed or were ripped by the rough concrete, the rush of air leaving the tire probably caused a bunch of other close-by polyester cords to rip as well, which is why it looks like a huge gash.
He also provided a summary for those of you who don’t want to read his full discussion:
barely any tread to start with -> wore through the nylon cap -> steel belt separation -> carcass ripped, air rushed out -> boom.
Ah, isn’t it great to have an engineer’s input to explain what’s going on instead of just ogling a YouTube video and saying “Huh, that looks neat”? I sure think so.
In any case, it’s a simple video concept, and the footage—while unique—is probably useless. Still, it’s the only time I’ve ever seen what the inside of a tire looks like during a burnout, and I have to appreciate that insight.